I really need help with this question! Please

I am soooo stuck with how to draw 2D cut lines from (b) in this solution set. I know its probably something really simple but its driving me crazy. I really don't know how to define the zeta cut lines and make a sketch as generated in the attachment. If someone could please give me some more detailed solution on how to complete step b I would really appreciate it.

I am just a beginner to COMSOL and I am really struggling with this - I have a test on Monday and I know that very similar concepts will be on the test. I am really panicking currently because I have been trying to figure this out for hours and I still can't do it ;(

Please help me.

Thank you a lot!